Am. J. Respir. Crit. Care Med., Vol 154, No. 3, Sep 1996, 665-669.
Comparison of respiratory inductance plethysmography with thoracoabdominal compression in bronchial challenges in infants and young children
C Springer, S Godfrey, D Vilozni, E Bar-Yishay, N Noviski and A Avital
Institute of Pulmonology, Hadassah University Hospital, Jerusalem, Israel.
Respiratory inductance plethysmography measuring thoracoabdominal
asynchrony (TAA) has been claimed to be a useful tool for measuring changes
in airway resistance in infants. In this study we evaluated the response to
methacholine by thoracoabdominal compression and respiratory inductance
plethysmography. Seventeen infants (mean age, 13.1 +/- 4.7 mo) with
recurrent episodes of cough or wheeze underwent bronchial challenge with
inhaled methacholine. Lung function was evaluated by measuring maximal
expiratory flow at resting lung volume (VmaxFRC), and the degree of TAA was
measured by phase angle (theta). Methacholine was inhaled for 1 min during
tidal breathing using increasing doubling concentrations until a fall of at
least 40% in VmaxFRC was achieved (final concentration). All infants
responded to the final concentration of methacholine by a significant fall
in VmaxFRC (from 31 +/- 10 to 12 +/- 5 ml/s/kg, p < 0.001). All but one
infant responded to methacholine at the final concentration with a
significant increase in phase angle (median theta increased from 11.7 to
31.7 degrees, p < 0.001). In two other infants there was an early
response in theta compared with the response in VmaxFRC. Phase angle
increase after methacholine was expressed as Z-scores (the difference
between postmethacholine theta and postbuffer theta divided by the standard
deviation of postbuffer theta). An increase of at least 2.0 Z- scores in
theta was observed at the same concentration of methacholine when VmaxFRC
fell by at least 40% in 15 of the 17 infants (88%). We conclude that
respiratory inductance plethysmography is a sensitive method to measure
bronchial reactivity to methacholine in most of the infants studied (14 of
17, 82%). A concentration of methacholine causing an increase in theta of
at least 2.0 standard deviations above baseline is equivalent to the
concentration causing a 40% fall in VmaxFRC.
